Off topic, but, offensive is ALWAYS for the person being offended. You don't get to pick and choose whether or not your words are offensive. That's up to other people. When someone tells you that your words have offended them, the proper response is to rephrase what you said to remove the offensive aspect. That's just good manners.
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To be honest, I see a lot of echoes of Egyptian mythology in the idea of the Wall of the Faithless. Egyptian myth, as I understand it, demands that every soul be judged before going on to the afterlife, with those failing judgement going to the Egyptian version of Hell. AFAIC, that's what the Wall represents. Since D&D has turned demons and devils into, essentially, parasites, and evil dead souls that followed a god don't get eaten by demons but are instead sent to whatever evil deity is most appropriate, the Wall represents those who have tried to reject reality.
See, the thing is, you could believe that the gods aren't really gods. But, that would require a conscious, deliberate choice. Pwyll the Impious Potter doesn't go to the wall - he accepts that the gods are real and are a thing, he's just not terribly concerned about the afterlife. For Pwyll to get the Wall, he'd have to deliberately choose to believe that the gods aren't actually gods. He's not just impious, he's outright unfaithful. I'm not sure of the details, but, it sounds like the Dragonborn that were added to FR don't just dislike the gods (which would be fine and counts as a kind of belief) but outright reject the gods and all they are.
However, at the end of the day, they are wrong. Not believing the gods are gods is kinda like not believing rain is wet. These are, in fact, gods. There is no great bait and switch to keep priests in power. There's no con going on here. The gods are, in fact, gods.
It was mentioned about evil gods. Thing is, if you get rid of the wall, the evil gods still don't get to torture the evil souls. The evil souls go off to whatever Hell is appropriate and they become the playthings of demons or devils. The evil gods only get to claim the souls of those who have given themselves to that god. However, since that would happen very, very rarely, the current system actually benefits evil gods. Those that are evil, but, not Faithless, get sent to whatever evil god is appropriate after cooling their heels in the Fugue Plane for a while. Otherwise, those souls would never actually be sent to any god's realms.
It's very much in the interest of the evil gods not to futz with the status quo.